1. Field of the Invention
The present invention relates to measuring, and, more particularly, to a device for positioning a gauge relative to a workpiece to be measured.
2. Description of the Related Art
Quality control techniques are commonly used to determine the dimensional accuracy and consistency of mass produced parts. One such technique involves placing a part or workpiece in a predetermined position on a measuring jig or fixture, placing a gauge in contact with the workpiece while holding the gauge in a predetermined position with respect to the fixture, and obtaining a reading from the gauge. This technique might be used to measure flatness, curvature, thickness, depth, height, or other dimensions or qualities.
It may frequently be desired to measure the dimensions along the edge of a plate or sheet workpiece. In the past, such measurements have been carried out by placing the workpiece on a fixture with spacers which space the edge of the workpiece a small distance away from the edge of the fixture and by inserting a tapered or stepped feeler gauge into the gap between the workpiece and the fixture.
In the case of a tapered feeler gauge, the gauge is inserted until the gauge is in contact with both the fixture and the workpiece. The height of the gap is determined from gradations marked on the gauge, and from this reading the corresponding dimension of the workpiece is calculated. The accuracy and repeatability of this technique depends largely on the force with which the tapered feeler gauge is inserted. Therefore, this technique is quite inaccurate when performed manually, as it usually is.
In the case of a stepped feeler gauge, the gauge is in the form of a rectangular plate having protruding or notched corners of known dimensions. The protrusions or notches are aligned with the gap between the fixture and the workpiece. A shim-type feeler gauge is used to fill in any remaining space between the stepped gauge and the workpiece. The readings on both gauges are summed to arrive at the desired measurement. The use of two gauges is cumbersome and prone to arithmetic errors. The accuracy is limited by size of the notches or steps.
Another approach to workpiece edge measurements has been the use of permanent or semi-permanent gauge holders attached to the fixture or a nearby structure. With this approach, the gauge holder includes a base, a swing arm pivotably mounted to the base, and a gauge positioner mounted at the end of the swing arm. In use, the workpiece is placed on the fixture with the swing arm pivoted out of the way. The mounting of the swing arm to the base is such that the arm may be swung into a predetermined position with respect to the fixture. A measuring gauge such as a spring-loaded retractable probe is placed in the positioner and brought into contact with the workpiece. A gauge reading is taken and the workpiece dimension determined. Measurements taken in this manner may be more precise and accurate; however, the gauge holders are complicated, expensive, and subject to wear and damage which impairs their reliability.
Therefore, there is a heretofore unmet need for a gauge positioner for use in measuring along the edge of a workpiece which is simply and economically constructed and which is capable of providing accurate, precise, and repeatable measurements.